1. Field
The following description relates generally to wireless communications and, more particularly, to a method for cooperative bandwidth aggregation using a MultiPath Transport Protocol.
2. Background
A MultiPath Transport Protocol (MPTP) allows support for multiple subflows or streams to be managed at the transport layer between a source and a destination on the internet. Examples of a MPTP include the MultiPath Transmission Control Protocol (TCP) and the Stream Control Transmission Protocol (SCTP). In particular, MultiPath Transmission Control Protocol (MPTCP) has been suggested to utilize multiple paths on the Internet between a source and a destination to aggregate performance across the paths. MultiPath TCP requires both the source and destination nodes to implement a MultiPath TCP compliant software stack. Many application servers on the Internet may have a legacy TCP stack. While a Client's TCP stack could be modified to be MultiPath TCP compliant, an application server may not have MultiPath TCP capability.
Wireless Wide Area Network (WWAN) Client nodes may be able to utilize multiple wireless carriers simultaneously. WWAN Client nodes can have multiple modems to access different wireless carriers with protocol stacks supporting the same wireless technology or different wireless technologies across the carriers. However, when using multiple carriers, the differential bandwidth across carriers and the inter-carrier skew between the carriers can be significant. Such an inter-carrier skew can vary typically over a range from 20 ms to 200 ms. The skew varies depending on where the traffic gets split in the WWAN infrastructure. For example, if the traffic across carriers gets split at an eNodeB where such an eNodeB serves multiple carriers both supporting Long Term Evolution (LTE), because the skew is local, the variation in the skew may be small. It is possible that tunneling may be required between eNodeBs in LTE for one or more paths, which can increase the skew across the paths. The differential bandwidth across paths can vary on the order of several tens to hundreds of kbps typically across multiple WWAN paths. Additionally, for example, if the traffic gets split at a Radio Network Controller (RNC) that serves different NodeBs in a WCDMA/UMTS/LTE network, or that serves different BTSs in a CDMA2000 network, each of which supports a different carrier for Wideband Code Division Multiple Access (W-CDMA)/UMTS or High Speed Packet Access (HSPA), then there can be additional variation in the differential bandwidth and skew across the paths can occur. Furthermore, the traffic may be split between RNCs and/or eNodeBs at a node higher up in the infrastructure that eventually serves the RNCs and/or eNodeBs and/or BNCs.
The differential bandwidth and skew across the paths can affect TCP performance when a single application flow for a WWAN Client utilizes multiple carriers. In such cases, MultiPath TCP would be useful to optimize the skew. However, an application server on the Internet for the other end-point of the TCP connection may not be MultiPath TCP compliant.